Golf ball with a large and soft polymer core

ABSTRACT

A golf ball includes a relatively large polymer core and has a soft ball compression. The polymer is, in the illustrated embodiments, a highly neutralized acid polymer. The golf ball may, optionally, include an outer core made of a different material, such as a thermoset polybutadiene rubber. The golf ball may, optionally, include a mantle layer made of an ionomer material. The inner core having a diameter of between 24 mm and 40 mm, and in some designs, between 28 mm and 32 mm, yields increased iron initial velocity and lower iron spin while maintaining driver performance.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation Application of, and claims priorityto, U.S. application Ser. No. 13/780,883, filed Feb. 28, 2013, whichclaims priority to U.S. Provisional Patent Application No. 61/606,856,filed on Mar. 5, 2012. The entire contents of each of these applicationsis hereby incorporated by reference.

BACKGROUND

The present invention relates generally to a golf ball having improvediron initial velocity and spin characteristics due to a large, softpolymer core.

The game of golf is an increasingly popular sport at both amateur andprofessional levels. A wide range of technologies related to themanufacture and design of golf balls are known in the art. Suchtechnologies have resulted in golf balls with a variety of playcharacteristics and durability. For example, some golf balls have abetter flight performance than other golf balls, in terms of initialvelocity, spin, and total distance.

In recent years, golf balls with high performance resins, in particular,highly neutralized polymer materials, have been introduced into themarket. While highly resilient and durable, highly neutralized polymermaterials may be costly and may feel hard to a golfer used to a ballmade of more traditional materials.

Therefore, there exists a need in the art for improvements in the use ofhighly neutralized polymers in golf balls.

SUMMARY

A golf ball includes a relatively large polymer core and has a soft ballcompression. The polymer is, in the illustrated embodiments, a highlyneutralized acid polymer. The golf ball may, optionally, include anouter core made of a different material, such as a thermosetpolybutadiene rubber. The golf ball may, optionally, include a mantlelayer made of an ionomer material. The inner core having a diameter ofbetween 24 mm and 40 mm, and in some embodiments, between 28 mm and 32mm, yields increased iron initial velocity and lower iron spin whilemaintaining driver performance.

In one aspect, the invention provides a golf ball comprising an innercore layer, wherein the inner core layer encompasses a center of thegolf ball. The ball includes a cover layer, wherein the cover layer ispositioned radially outward of the inner core layer and substantiallysurrounds the inner core layer. The inner core layer comprises a highlyneutralized polymer. The inner core layer has an inner core diameterbetween 28 mm and 40 mm.

In another aspect, the invention provides a golf ball comprising aninner core layer, wherein the inner core layer encompasses a center ofthe golf ball. A cover layer positioned radially outward of the innercore layer and substantially surrounds the inner core layer. The innercore layer consists essentially of a single formulation of a highlyneutralized polymer, additives, fillers, and melt flow modifiers. Theinner core layer has a hardness, which is about 66 JIS C. The inner corelayer has an inner core diameter between 24 mm and 40 mm.

Other systems, methods, features and advantages of the invention willbe, or will become, apparent to one of ordinary skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be included within this description and this summary, bewithin the scope of the invention, and be protected by the followingclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention. Moreover, in the figures, likereference numerals designate corresponding parts throughout thedifferent views.

FIG. 1 shows a first representative golf ball in accordance with thisdisclosure, the golf ball being of a two-piece construction;

FIG. 2 shows a second representative golf ball in accordance with thisdisclosure, the golf ball being of a three-piece construction, having acore, a mantle layer, and an outer cover layer;

FIG. 3 shows a third representative golf ball in accordance with thisdisclosure, the golf ball being of a three-piece construction, having aninner core layer, an outer core layer, and an outer cover layer;

FIG. 4 shows a fourth representative golf ball in accordance with thisdisclosure, the golf ball being of a three-piece construction, having aninner core layer, an outer core layer, a mantle layer, and an outercover layer;

FIG. 5 is a table showing construction and material properties ofvarious four-piece balls;

FIG. 6 is a table showing tested performance characteristics of thevarious four-piece balls shown in FIG. 5 and a popular rubber core ball;and

FIG. 7 is a table showing tested durability of selected balls from FIG.5.

DETAILED DESCRIPTION

Generally, this disclosure relates to a golf ball that includes arelatively large, soft polymer core. The polymer is, in the illustratedembodiments, a highly neutralized polymer (HNP). The polymer may, insome embodiments, may be a formulation having a single HNP formulation,namely only HPF AD1035 and additives, fillers, and melt flow modifiers.The inner core is intended to be soft, having a hardness between 65 and72 JIS C. The golf ball may, optionally, include an outer core made of adifferent material, such as a thermoset polybutadiene rubber. The golfball may, optionally, include a mantle layer made, in some embodiments,of an ionomer material. The inner core having a diameter of between 24mm and 40 mm, and in some embodiments, between 28 mm and 32 mm andbetween 28 and 40 mm, yields increased iron initial velocity and loweriron spin while maintaining driver performance. The ball compression isgenerally soft, being between is between 2.65 and 2.72.

As used herein, unless otherwise stated, certain material properties andgolf ball properties are defined as follows.

The term “hardness” as used herein is measured generally in accordancewith ASTM D-2240 and JIS K 6253. The hardness of a material is taken asthe slab hardness, while the hardness of a golf ball component ismeasured on the curved surface of the molded golf ball component. When ahardness measurement is made on a dimpled cover, hardness is measured ona land area of the dimpled cover. Hardness units are generally given inShore D, Shore C, and JIS C, as indicated.

The “coefficient of restitution” or “COR” is measured generallyaccording to the following procedure: a test object is fired by an aircannon at an initial velocity of 40 m/sec, and a speed monitoring deviceis located over a distance of 0.6 to 0.9 meters from the cannon. Afterstriking a steel plate positioned about 1.2 meters away from the aircannon, the test object rebounds through the speed-monitoring device.The return velocity divided by the initial velocity is the COR.

The “flexural modulus” is measured generally in accordance with ASTMD-790.

The “Vicat softening temperature” is measured generally in accordancewith ASTM D-1525.

The “compression deformation” herein indicates the deformation amount ofthe ball under a force; specifically, when the force is increased tobecome 130 kg from 10 kg, the deformation amount of the ball under theforce of 130 kg subtracts the deformation amount of the ball under theforce of 10 kg to become the compression deformation value of the ball.All of the tests herein are performed using a compression testingmachine available from Automated Design Corp. in Illinois, USA (ADC).The ADC compression tester can be set to apply a first load and obtain afirst deformation amount, and then, after a selected period, apply asecond, typically higher load and determine a second deformation amount.Thus, the first load herein is 10 kg, the second load herein is 130 kg,and the compression deformation is the difference between the seconddeformation and the first deformation. Herein, this distance is reportedin millimeters. The compression can be reported as a distance, or as anequivalent to other deformation measurement techniques, such as Atticompression. While the ADC compression testing machine identified abovecan be programmed to perform these compression tests, these types ofcompression tests may also be performed on a testing machine availablefrom EKTRON TEK Co., LTD.; Model name: EKTRON-2000 GBMD-CS.

Except as otherwise discussed herein below, any golf ball discussedherein may generally be any type of golf ball known in the art. Namely,unless the present disclosure indicates to the contrary, a golf ball maygenerally be of any construction conventionally used for golf balls,such as a conforming or non-conforming construction. Conforming golfballs are golf balls that meet the Rules of Golf as approved by theUnited States Golf Association (USGA). Golf balls discussed herein mayalso be made of any of the various materials known to be used in golfball manufacturing, except as otherwise noted.

Furthermore, it is understood that any feature disclosed herein(including but not limited to elements of the various embodiments shownin the FIGS. and various chemical formulas or mixtures) may be combinedwith any other features disclosed here, as may be desired, in anycombination, sub-combination, or arrangement.

Finally, as used herein, the terms “about” and “substantially” areintended to account for engineering and manufacturing tolerances.

A golf ball made in accordance with this disclosure may generally haveany solid golf ball construction, as long as the innermost core includesthe large core as described herein. The materials of the other layer(s)of the golf ball may be any material known in the art. FIG. 1 shows afirst golf ball 100 having aspects in accordance with this disclosure.Golf ball 100 is a two-piece golf ball. Specifically, golf ball 100includes first outer cover layer 110 substantially surrounding firstcore 120.

FIG. 2 shows a second golf ball 200 having aspects in accordance withthis disclosure. Golf ball 200 includes a second core 230, a secondmantle layer 220 substantially surrounding second core 230, and a secondouter cover layer 210 substantially surrounding second mantle layer 220.

FIG. 3 shows a third golf ball 300 having aspects in accordance withthis disclosure. Golf ball 300 includes a third inner core 330, a thirdouter core 320 substantially surrounding third inner core 330, and athird outer cover layer 310 substantially surrounding third outer corelayer 320.

Generally, in multi-piece constructions, the term “core” as used hereinrefers to at least one of the innermost structural components of thegolf ball. The term core may, for example, refer to (1) third inner core330 only, (2) both third inner core 330 and third outer core 320collectively, or (3) third outer core 320 only. The term core may alsoencompass more than two layers if, for example, an additional structurallayer is present between third inner core 330 and third outer core 320or encompassing third outer core 320.

FIG. 4 shows a fourth golf ball 400 having aspects in accordance withthis disclosure. Fourth golf ball 400 is a four-piece golf ball. Fourthgolf ball 400 includes a fourth inner core layer 440, a fourth outercore layer 430 substantially surrounding fourth inner core layer 440, afourth mantle layer 420 substantially surrounding fourth outer corelayer 430, and a fourth outer cover layer 410 substantially surroundingfourth mantle layer 420.

Additional embodiments, not shown, may have more layers or pieces. Forexample, additional core layers and/or additional cover layers may bepresent to form five, six, seven, or even higher piece balls.

The various layers of golf balls according to the various embodimentsmay be made from any known golf ball material. However, the innermostcore layer, such as first core 120, second core 220, third inner corelayer 330, and fourth inner core layer 440, is made of a polymermaterial. In some embodiments, the polymer material is an ionomer.

An ionomer is generally understood as any polymer material that includesionized functional groups therein. Ionomeric resins are often ioniccopolymers of an olefin and a salt of an unsaturated carboxylic acid.The olefin may have from about 2 to about 8 carbon atoms, and may be analpha-olefin. The acid may be an unsaturated monocarboxylic acid havingfrom about 3 to about 8 carbon atoms, and may be an alpha,beta-unsaturated carboxylic acid. Commonly, ionomers are copolymers ofethylene and either acrylic acid or methacrylic acid. In somecircumstances, an additional co-monomer (such as an acrylate ester,i.e., iso- or n-butylacrylate, etc.) can also be included to produce aterpolymer. A wide range of ionomers are known to the person of ordinaryskill in the art of golf ball manufacturing.

When a large portion of the acid groups in the ionomer is neutralized bya cation, the ionomer material may be considered to be a highlyneutralized acid polymer. Generally, such a polymer is considered highlyneutralized when at least 70% of the acid groups are neutralized by acation. In various embodiments, the highly neutralized acid polymer maybe neutralized to at least 75%, at least 80%, at least 85%, at least90%, at least 95%, at least 98%, at least 99%, or substantially 100%.

The acid content of an ionomer, including highly neutralized polymers,is defined as the percentage of unsaturated carboxylic acid by weightrelative to the total weight of the polymer. Generally, the acid contentmay range from 1% to 50%. In general, the acid content is considered“low” when the acid content does not exceed 15%. The acid content isconsidered “medium” when the acid content is greater than about 15% andless than about 18%. The acid content is considered “high” when the acidcontent is equal to or greater than 18%. In some embodiments, the acidcontent is considered high when between 18% and 50% or between 18% and40%. Generally, higher acid levels may enable higher densities, buthigher acid levels may also result in a loss of melt-processability andrelated properties such as elongation and toughness. Namely, high acidlevels may reduce any crystallinity otherwise present in the polymer.

In the illustrated embodiments, the innermost core layer, whichencompasses a center of the golf ball, such as first core 110, secondcore 220, third inner core layer 330, and fourth inner core layer 440,is made from highly neutralized polymer compositions, sometimes calledhighly neutralized acid polymers or highly neutralized acid polymercompositions, and fillers. In some embodiments, only one type orformulation of highly neutralized polymer is used, while in otherembodiments, blends of different types or formulations of highlyneutralized polymers in various percentages are used. The innermost corelayer may be made using any technique known in the art, including butnot limited to injection molding.

In some embodiments, the innermost core layers generally include one ortwo highly neutralized polymer compositions with additives, fillers, andmelt flow modifiers. In some embodiments, the innermost core layergenerally includes HPF resins such as HPF2000 and HPF AD1035, producedby E. I. DuPont de Nemours and Company. In some embodiments, theinnermost core layer includes 100% by weight of HPF AD1035. In someembodiments, the innermost core layer includes 80% by weight of HPFAD1035 and 20% by weight of additives, fillers, and melt flow modifiers.In some embodiments, the innermost core layer includes 70% by weight ofHPF AD1035 and 30% by weight of HPF2000. In some embodiments, theinnermost core layer includes 60% by weight of HPF AD1035, 20% by weightof HPF2000, and 20% by weight of additives, fillers, and melt flowmodifiers. In some embodiments, the relative percentages of HPF AD1035,HPF2000, and additives, fillers, and melt flow modifiers may change,with HPF2000 ranging from 0% to 100% by weight of the composition, HPFAD1035 ranging from 0% to 100% by weight of the composition, and/oradditives, fillers, and melt flow modifiers ranging from 0% to about 25%by weight of the composition.

In some embodiments, the innermost core layer is intended to be soft toimprove the feel and driver distance for lower club head speeds. In someembodiments, the JIS C hardness of the innermost core layer is between65 and 75. In some embodiments with a blend of 40% HPF2000, 40% HPFAD1035, and 20% additives, fillers, and melt flow modifiers, the JIS Chardness is about 72. In some embodiments with a blend of 20% HPF2000,60% HPF AD1035, and 20% additives, fillers, and melt flow modifiers, theJIS C hardness is about 69. In some embodiments with 80% HPF AD1035 and20% additives, fillers, and melt flow modifiers, the JIS C hardness isabout 66. In some embodiments, the hardness is the same throughout theinnermost core layer, as the innermost core layer is substantiallyhomogeneous. As the percentage of HPF AD1035 increases, the hardnessgenerally decreases. The relationship of hardness to percentage HPFAD1035 is generally linear. In some embodiments, if H is the hardnessand P is the percentage of HPF AD1035 in the inner core layercomposition, the relationship between H and P is given by the followingequation, Eq. 1, within standard engineering/manufacturing tolerances:H=78−0.12P  Eq. 1

Suitable additives and fillers may include, for example, blowing andfoaming agents, optical brighteners, coloring agents, fluorescentagents, whitening agents, UV absorbers, light stabilizers, defoamingagents, processing aids, mica, talc, nanofillers, antioxidants,stabilizers, softening agents, fragrance components, plasticizers,impact modifiers, acid copolymer wax, surfactants. Suitable fillers mayalso include inorganic fillers, such as zinc oxide, titanium dioxide,tin oxide, calcium oxide, magnesium oxide, barium sulfate, zinc sulfate,calcium carbonate, zinc carbonate, barium carbonate, mica, talc, clay,silica, lead silicate. Suitable fillers may also include high specificgravity metal powder fillers, such as tungsten powder and molybdenumpowder. Suitable melt flow modifiers may include, for example, fattyacids and salts thereof, polyamides, polyesters, polyacrylates,polyurethanes, polyethers, polyureas, polyhydric alcohols, andcombinations thereof.

Previously, it was believed that having the innermost core of a golfball made from HPF AD1035 without HPF 2000 in some percentage as a dualHNP blend would lack sufficient durability for use as a golf ball corematerial. However, it is now understood by the inventors that having aninnermost core composition containing only HPF AD1035 and any desiredadditives, fillers, and melt flow modifiers is appropriate for use in agolf ball core. This understanding is borne out by the testing ofvarious balls made according to this disclosure, as detailed in FIG. 5,discussed below. Use of only HPF AD1035 is advantageous, due the abilityto achieve a softer compression over HPF 2000 cores or cores havingblends containing both HPF AD1035 and HPF 2000.

In some of the embodiments, the innermost core diameter, such as thediameter of third inner core layer 330 and fourth inner core layer 440,is between 20 mm and 28 mm, which range is considered by the inventorsto be a normal range for innermost cores containing highly neutralizedpolymers. Previously, it was believed that if an inner core were made ofhighly neutralized polymers and the inner core diameter were greaterthan about 28 mm, then the feel may be too hard and the ball may spintoo much, thereby decreasing driver distance. However, it is nowunderstood by the inventors that having an inner core diameter ofbetween 28 mm and 40 mm may be advantageous in terms of durability whilehaving no detrimental impact on driver distance. These advantages may beparticularly apparent when the composition of the innermost coreincludes only HPF AD1035 and additives, fillers, and melt flow modifiers(i.e., no HPF2000 in the inner core composition), since it waspreviously believed that HPF AD1035 only cores lacked durability. Thetest data for the examples, below, verifies this new, unexpectedunderstanding.

If provided, an outer core layer, such as third outer core 320, as shownin FIG. 3, and fourth outer core 430, as shown in FIG. 4, generallysurrounds and encloses the inner core layer, such as third inner core330, as shown in FIG. 3, and fourth inner core 440, as shown in FIG. 4.The outer core layer in some embodiments has a thickness of at least 4.8mm. In those embodiments where the inner core layer is made of a singlehighly neutralized polymer with additives, fillers, and melt flowmodifiers and having a diameter ranging from 20 mm-28 mm, if thethickness of the outer core layer is less than about 4.8 mm, it isbelieved by the inventors that the feel of the golf ball may be too hardand may produce too much spin. It is believed by the inventors that thebeneficial performance and aesthetic characteristics are maximized whenthe thickness of the outer core layer ranges from 5.0 mm to 8 mm. Insome embodiments, the diameter of the core (the inner core layer and theouter core layer together) ranges from about 34 mm to about 40 mm. Inembodiments where the inner core layer is made of a highly neutralizedpolymer composition having a diameter ranging from greater than 28 mm toless than 40 mm, the outer core layer thickness may be selected tomaintain an overall core diameter of 34 mm to 40 mm. In any of theembodiments described herein, the outer core layer thickness may beselected to have a conforming golf ball, where the total diameter of thegolf ball does not exceed 1.68 inches.

The outer core layer may be made using any material, but in someembodiments is made of a thermoset polybutadiene rubber. In someembodiments, the outer core layer is generally formed by crosslinking apolybutadiene rubber composition as described in U.S. Patent PublicationNumber 2012/0004052, the disclosure of which is hereby incorporated byreference in its entirety. Various additives may be added to the baserubber to form a compound. The additives may include a cross-linkingagent and a filler. In some embodiments, the cross-linking agent may bezinc diacrylate, magnesium acrylate, zinc methacrylate, or magnesiummethacrylate. In some embodiments, zinc diacrylate may provideadvantageous resilience properties. The filler may be used to alter thedensity of the material. The filler may include zinc oxide, bariumsulfate, calcium carbonate, or magnesium carbonate. In some embodiments,zinc oxide may be selected for its advantageous properties. Metalpowder, such as tungsten, may alternatively be used as a filler toachieve a desired density. In some embodiments, the density of the outercore layer may be from about 1.05 g/c{circumflex over (m)}3 to about1.45 g/c{circumflex over (m)}3. In some embodiments, the density of theouter core layer may be from about 1.05 g/c{circumflex over (m)}3 toabout 1.35 g/c{circumflex over (m)}3.

In some embodiments, a polybutadiene synthesized with a rare earthelement catalyst may be used to form the outer core layer. Such apolybutadiene may provide excellent resilience performance of the golfball. Examples of rare earth element catalysts include lanthanum seriesrare earth element compound, organoaluminum compound, and almoxane andhalogen containing compounds. Polybutadiene obtained by using lanthanumrare earth-based catalysts usually employs a combination of a lanthanumrare earth (atomic number of 57 to 71) compound, such as a neodymiumcompound.

In some embodiments, a polybutadiene rubber composition having at leastfrom about 0.5 parts by weight to about 5 parts by weight of ahalogenated organosulfur compound may be used to form the outer corelayer. In some embodiments, the polybutadiene rubber composition mayinclude at least from about 1 part by weight to about 4 parts by weightof a halogenated organosulfur compound. The halogenated organosulfurcompound may be selected from the group consisting ofpentachlorothiophenol; 2-chlorothiophenol; 3-chlorothiophenol;4-chlorothiophenol; 2,3-chlorothiophenol; 2,4-chlorothiophenol;3,4-chlorothiophenol; 3,5-chlorothiophenol; 2,3,4-chlorothiophenol;3,4,5-chlorothiophenol; 2,3,4,5-tetrachlorothiophenol;2,3,5,6-tetrachlorothiophenol; pentafluorothiophenol;2-fluorothiophenol; 3-fluorothiophenol; 4-fluorothiophenol;2,3-fluorothiophenol; 2,4-fluorothiophenol; 3,4-fluorothiophenol;3,5-fluorothiophenol 2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol;2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol;4-chlorotetrafluorothiophenol; pentaiodothiophenol; 2-iodothiophenol;3-iodothiophenol; 4-iodothiophenol; 2,3-iodothiophenol;2,4-iodothiophenol; 3,4-iodothiophenol; 3,5-iodothiophenol;2,3,4-iodothiophenol; 3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol;2,3,5,6-tetraiodothiophenol; pentabromothiophenol; 2-bromothiophenol;3-bromothiophenol 4-bromothiophenol; 2,3-bromothiophenol;2,4-bromothiophenol; 3,4-bromothiophenol; 3,5-bromothiophenol;2,3,4-bromothiophenol; 3,4,5-bromothiophenol;2,3,4,5-tetrabromothiophenol; 2,3,5,6-tetrabromothiophenol; and theirzinc salts, the metal salts thereof and mixtures thereof.

The outer core layer may be made by any suitable process. For example,in some embodiments, the outer core layer may be made by a compressionmolding process. The process of making the outer core layer may beselected based on a variety of factors. For example, the process ofmaking the outer core layer may be selected based on the type ofmaterial used to make the outer core layer and/or the process used tomake the other layers.

In some embodiments, the outer core layer may be made through acompression molding process including a vulcanization temperatureranging from 130° C. to 190° C. and a vulcanization time ranging from 5to 20 minutes. In some embodiments, the vulcanization step may bedivided into two stages: (1) the outer core layer material may be placedin an outer core layer-forming mold and subjected to an initialvulcanization so as to produce a pair of semi-vulcanized hemisphericalcups and (2) a prefabricated inner core layer may be placed in one ofthe hemispherical cups and may be covered by the other hemispherical cupand vulcanization may be completed. In some embodiments, the surface ofthe inner core layer placed in the hemispherical cups may be roughenedbefore the placement to increase adhesion between the inner core layerand the outer core layer. In some embodiments, inner core surface may bepre-coated with an adhesive before placing the inner core layer in thehemispherical cups to enhance the durability of the golf ball and toenable a high rebound.

In some embodiments, the outer core layer may have a surface Shore Dhardness of from 50 to 60 or a JIS C hardness of from 80 to 87, whichmay be higher than the surface hardness of the inner core layer. In someembodiments, the outer core layer may have a surface JIS C hardness ofat least 85.5. In some embodiments, the outer core layer may have asurface Shore D hardness of from 45 to 55. In some embodiments, theouter core layer has a Shore D hardness of at least 55.

In some embodiments, such as the embodiments shown in FIG. 2 and FIG. 4,a mantle layer may be provided, such as second mantle layer 220 andfourth mantle layer 420. The mantle layer generally surrounds andencloses the outermost core layer, such as second core 220 and fourthouter core layer 430. In some embodiments, the mantle layer is made of athermoplastic material, discussed further below. In some embodiments,the mantle layer has a Shore D hardness, as measured on the curvedsurface, ranging from about 50 to about 70, and in some embodimentsranging from about 55 to 64. In some embodiments, the mantle layer has aJIS C hardness, as measured on the curved surface, ranging from about 80to 90 and in some embodiments from about 83 to about 89.

In some embodiments, the mantle layer has the highest specific gravityof any layer in the golf ball. In some embodiments, the mantle layer hasa specific gravity ranging from about 1.10-about 1.17. A high specificgravity for the mantle layer improves the moment of inertia overcommercially available high performance golf balls by shifting the massof the golf ball toward the outermost surface of the golf ball.

In some embodiments, the mantle layer is made from a thermoplasticmaterial including at least one of an ionomer resin, a highlyneutralized polymer composition, a polyamide resin, a polyester resin,and a polyurethane resin. In some embodiments, the mantle layer isSurlyn®. In some embodiments, the Surlyn used in the mantle layer isnormal acid, having an acid content that does not exceed about 15% byweight. In some embodiments, the Surlyn used in the mantle layer ismedium acid, which is greater than about 15% but less than about 18%. Insome embodiments, the Surlyn used in the mantle layer is high acid,having an acid content of between 18% and 50% by weight. In someembodiments, the high acid Surlyn of the mantle has an acid content ofabout 20% by weight.

The mantle layer may have any desired thickness. In some embodiments,the mantle thickness may be selected so that the golf ball is aconforming golf ball. In some embodiments, the mantle thickness isbetween 0.5 and 1.3 mm. In some embodiments, the mantle thickness isbetween about 0.95 mm and about 1.2 mm. In some embodiments, the mantlethickness is between about 0.5 mm and 0.95 mm. In some embodiments, themantle thickness is about 0.6 mm. In some embodiments, the mantlethickness is about 0.95 mm. In some embodiments, the mantle thickness isabout 1.2 mm.

The combination of acid level and thickness for the mantle layer mayimpact performance. In some embodiments, the mantle material is normalacid and has a thickness of about 0.95 mm. In some embodiments, themantle material is high acid and has a thickness of about 0.95 mm. Insome embodiments, the mantle material is high acid and has a thicknessof about 1.2 mm. In some embodiments, the mantle material is normal acidand has a thickness of about 1.2 mm. In some embodiments, the mantlematerial is normal acid and has a thickness of about 0.6 mm. In someembodiments, the mantle material is high acid and has a thickness ofabout 0.6 mm.

The outer cover layer, such as first cover layer 110 of FIG. 1, secondcover layer 210 of FIG. 2, third outer cover layer 310 of FIG. 3, andfourth outer cover layer of FIG. 4, may be made of any material known inthe golf ball art, including but not limited to ionomers such asSurlyn®, urethanes, thermoplastic polyurethanes, balata, andcombinations of these materials. In some embodiments, the outer coverlayer material is a blend of PTMEG, BG, TMPME, DCP, and MDI in varyingpercentages by weight. “PTMEG” is polytetramethylene ether glycol,having a number average molecular weight of 2,000, and is commerciallyavailable from Invista, under the trade name of Terathane® 2000. “BG” is1,4-butanediol, commercially available from BASF and other suppliers.“TMPME” is trimethylolpropane monoallylether, commercially availablefrom Perstorp Specialty Chemicals AB. “DCP” is dicumyl peroxide,commercially available from LaPorte Chemicals Ltd. “MDI” isdiphenylmethane diisocyanate, commercially available from Huntsman,under the trade name of Suprasec® 1100. Specifically, these materialsmay be prepared by mixing the components in a high agitated stir for oneminute, starting at a temperature of about 70° C., followed by a 10-hourpost curing process at a temperature of about 100° C. The post curedpolyurethane elastomers may be ground into small chips.

Other suitable outer cover layer compositions are disclosed in thefollowing patent documents, each of which is incorporated herein in itsentirety: U.S. Patent Application Publication No. 2012/0004050 toYasushi Ichikawa et al., filed on Jan. 5, 2012; U.S. Patent ApplicationPublication No. 2013/0172104 to Thomas J. Kennedy III, filed on Dec. 30,2011; and U.S. Patent Application Publication No. 2013/0172122 toYasushi Ichikawa et al., filed on Jan. 3, 2012.

The outer cover layer may be manufactured using any known technique,including but not limited to injection molding, RIM, and compressionmolding.

In some embodiments, the outer cover layer may have a Shore D hardness,as measured on the curved surface, ranging from about 50 to about 70. Insome embodiments, the outer cover layer may have a Shore D hardness, asmeasured on the curved surface, ranging from about 58 to about 64. Insome embodiments, the outer cover layer may have a JIS C hardness, asmeasured on the curved surface, ranging from about 85 to about 95. Insome embodiments, the outer cover layer has a JIS C hardness, asmeasured on the curved surface, ranging from about 89 to about 92.

To have a low spin performance off the driver shot and good hittingfeel, the mantle layer may have a higher flexural modulus than the outercover layer. In some embodiments, the mantle layer may have a flexuralmodulus ranging from 50,000 psi to 100,000 psi, or from 60,000 psi to100,000 psi and outer cover layer 140 may have a flexural modulusranging from 200 psi to 3,000 psi, or from 300 psi to 2,000 psi. In someembodiments, the mantle layer may have a first flexural modulus and theouter cover layer may have a second flexural modulus, and a ratio offirst flexural modulus to second flexural modulus (first flexuralmodulus/second flexural modulus) may range from 10 to 30. In someembodiments, ratio of first flexural modulus to second flexural modulus(first flexural modulus/second flexural modulus) may range from 25 to100. In some embodiments, the ratio of first flexural modulus to secondflexural modulus (first flexural modulus/second flexural modulus) mayrange from 95 to 250. In some embodiments, the inner core layer may havea third flexural modulus. In some embodiments, the ratio of firstflexural modulus to third flexural modulus (third flexuralmodulus/second flexural modulus) may range from 5 to 10. The outer coverhaving a lower flexural modulus than the mantle layer and/or the innercore layer may provide the golf ball with a good feel in short shots andputting shots.

The thickness of the outer cover layer may be any desired thickness. Insome embodiments, the thickness of the outer cover layer is selected toallow the golf ball to be a conforming golf ball. In some embodiments,the thickness of the outer cover layer is selected to enhance the feelof the golf ball. In some embodiments, the thickness of the outer coverlayer is between about 0.5 mm to about 1.5 mm. In some embodiments, thethickness of the outer cover layer is about 1.1 mm.

Golf balls according to this disclosure are provided with dimples on theouter cover layer to enhance the aerodynamic performance of the golfball. Any number of dimples having any shape and depth and in anypattern known in the art may be provided on outer cover layer. In someembodiments, between 200 and 500 hemispherical dimples may be provided.In some embodiments, between 300 and 400 dimples may be provided. Insome embodiments, between 320 and 350 dimples may be provided.

In some embodiments, one or more coating layers may be applied to outercover layer. The coating layer(s) may be provided for any reason, suchas for altering a hardness of the outer cover layer, altering theaerodynamics of the golf ball, enhancing the visibility of the golfball, and for aesthetic purposes. The coating may be any type of coatingknown in the art, including but not limited to paints, inks, clearcoats, urethane coatings, sparkle coatings, and the like. The coatingmay be applied using any method known in the art, including but notlimited to spraying, stamping, pad printing, brush applications,combinations of these techniques, and the like.

Once assembled, golf balls according to the present disclosure willexhibit various characteristics based upon the construction. Some ofthese characteristics include a ball COR, a ball weight, and a ballcompression. In some embodiments, the ball COR ranges from about 0.78 toabout 0.79. In some embodiments, the ball COR ranges from about 0.7838to about 0.7892.

In some embodiments, the ball compression is intended to be soft for asofter feel as compared with other golf balls that use HNP as a corematerial. A softer compression may also allow for longer driver distancefor golfers with lower club head speeds. In some embodiments, the ballcompression may range from about 2.4 to about 2.75. In some embodiments,the ball compression may range from about 2.43 to about 2.69.

Example

FIG. 5 shows a table of four-piece balls having differing constructions,but each made in accordance with the teachings of this disclosure. Theballs of FIG. 5 are generally constructed according to FIG. 4, with aninner core layer, an outer core layer, a mantle layer, and an outercover layer. Each of these balls, then, may be considered to be specificembodiments of the disclosure, which are believed to have someperformance difference as compared to existing golf balls. Each of thesegolf balls was manufactured using well known techniques that includeinjection molding the inner core layer, compression molding the outercore layer around the inner core layer to form a core, injection moldingthe mantle layer onto the core, then injection molding the outer coverlayer onto the mantle layer.

Example 1 is a ball made according to the embodiments with largeinnermost core layers. Specifically, Example 1 has an innermost coresize of 28.1 mm. Example 1 and Example 2 are balls made according to theembodiments without HPF2000. Specifically, Example 1 and Example 2 aremade with 80% by weight of HPF AD1035 and 20% by weight of additives,fillers, and melt flow modifiers. Example 1 and Example 2 have the sameinner core formulation and the same construction for the rest of thelayers. The only difference between Example 1 and Example 2 is the innercore diameter: Example 1 has a large inner core diameter of 28.1 mmwhile Example 2 has a “normal” HNP core diameter of 24.5 mm.

The rest of the balls, Comp 1, Comp 2, Comp 3, Comp 4, Comp 5, Comp 6,Comp 7, and Comp 8, are somewhat similarly constructed balls withvariations in the construction as indicated, but have innermost coresizes that do not exceed 24.5 mm. All of the balls in FIG. 5 havepolymer cores formed of highly neutralized polymers. Specifically, allof the golf balls in FIG. 5 include HPF compounds, particularly HPF2000and HPF AD1035. While most of the golf balls in FIG. 5 include a blendof HPF2000 and HPF AD1035, two of the balls, Example 1 and Example 2 donot include HPF2000. Example 1 and Example 2 both have only HPF AD1035and additives, filler, and melt flow modifiers.

All of the balls in FIG. 5 include outer cores of polybutadiene rubber.All of the balls in FIG. 5 include mantle layers of Surlyn®. However,some of the balls in FIG. 5 are made with normal acid Surlyn (Comp 6,Comp 7, and Comp 8) while others are made with high acid Surlyn (Example1, Example 2, Comp 1, Comp 2, Comp 3, Comp 4, and Comp 5.)

Testing

FIG. 6 shows test results for the balls in FIG. 5. In addition to thegolf ball constructions shown in FIG. 5, a popular, high performance,commercially available four-piece, dual rubber core ball was tested,labeled in FIG. 6 as Rubber Core.

All of the golf balls were tested using a swing robot. Various clubsthrough the bag were tested: a 6 iron, a 9 iron, a driver, a 3 iron, anda wedge. The 6 iron used in the testing is a VR Pro Si blade with a 16.7degree loft, commercially available from Nike Golf (Nike, Inc.) ofBeaverton, Oreg. The club head speed for the 6 iron test is about 96mph. The 9 iron used in the testing is a VR Pro 8i blade, commerciallyavailable from Nike Golf. The club head speed for the 9 iron test isabout 91 mph. The driver used in the testing is Model TI-360 USGAavailable from Fu Sheng Industrial Co., Ltd., with the robot swing speedset to be 120 mph. The 3 iron used in the testing is a VR Pro 3i blade,commercially available from Nike Golf. The wedge for the 70 yd pitchtest is a VR Pro x3xhad a loft of 60 degrees. For iron testing, the facelocation is centered left to right and on the 5th to 6th groove, countedfrom the bottom.

The following parameters were measured: initial velocity (IV) in milesper hour, launch angle (LA) in degrees, backspin (BS) in revolutions perminute, and total distance (for the driver) in yards. These measurementswere obtained using standard launch monitor and distance measurementtechniques. In this test, a GC2 Smart Camera System, commerciallyavailable from Foresight Sports of San Diego, Calif., was used.

The testing data shows, among other conclusions, that Example 1 providesincreased iron initial velocity and decreased iron backspin comparedwith the other balls having HNP cores. For example, when hit with a 6iron, Example 1 has an initial velocity of almost 2 mph greater thanComp 5. Comp 5 has a blended HPF2000 and HPF AD1035 inner core of 24.5mm and a thin, high acid mantle layer of 0.6 mm. Example 1 has an innercore with only HPF AD1035 and additives, fillers, and melt flowmodifiers of 28.1 mm and a thicker, high acid mantle layer of 1.2 mm.Additionally, the backspin of Example 1 is 570 rpm less than that ofComp 5.

Similarly, when hit with a 6 iron, Example 1 has an initial velocity ofalmost 1 mph greater than Example 2. The only construction differencebetween Example 1 and Example 2 is inner core size, where Example 1 hasa larger inner core than Example 2. Increased initial velocity is foundfor all of the irons for these two balls. Therefore, the inventors haveconcluded that a larger inner core layer increases iron initialvelocity, when the only HNP present in the inner core layer is HPFAD1035. Additionally, the backspin of Example 1 when hit with a 6 ironis 681 rpm less than that of Example 2. Backspin reductions are foundfor all of the irons for these two balls. Therefore, the inventors haveconcluded that a larger inner core layer decreases iron backspin,particularly mid-iron backspin, when the only HNP present in the innercore layer is HPF AD1035.

Example 2 and Comp 1 are similarly constructed, with the main differencebeing that the inner core layer of Example 2 includes only HPF AD1035and additives, fillers, and melt flow modifiers, while Comp 1 has aninner core layer that includes a blend of HPF2000 and HPF AD1035. Whenhit with a 6 iron, the initial velocity of Example 2 is slightly greaterthan that of Comp 1. However, the initial velocity of Example 1, whichhas the same inner core layer material as Example 2 but a largerdiameter inner core, is more than 1 mph greater than that of Comp 1.Therefore, the inventors have concluded that the combination of a largerinner core layer having only HPF AD1035, additives, fillers, and meltflow modifiers maximizes the increase in initial velocity over smallerinner core layers made from a blend of HPF 2000 and HPF AD1035 asopposed to just shifting the inner core layer material from the blend tojust HPF AD1035.

It is of note that the iron initial velocities, iron backspins, anddriver initial velocities, backspins, and total distance are similar tothe same parameters of the Rubber Core ball.

In addition to the above parameters, durability was tested. Thedurability was tested by repeatedly performing a COR test with the sameball for as many shots as possible until the ball failed or reached 150shots. For example, if a material layer failed in any way, such asdelamination with adjacent layers, buckling of the material, fracturingor cracking of the material, etc., the ball would “deaden.” Thisdeadening of the ball is detectable in a variety of ways, but for thepurposes of this testing, was determined by monitoring the COR. If theball deadens, the COR will noticeably and suddenly reduce.

FIG. 7 shows the durability results for selected balls from FIG. 5,indicating either the number of shots achieved prior to the balldeadening or measuring the difference between the COR on the first shotand the COR on shot 150. Of particular interest is the difference indurability between Example 1 and Example 2. As suspected by theinventors, Example 2, which has an innermost core made with acomposition of only HPF AD1035 and additives, fillers, and melt flowmodifiers, lacked sufficient durability to be tested for 150 shots.Example 2 has an inner core diameter of 24.5, which falls into a rangeconsidered standard prior to this research. Example 2 failed after 118shots. However, Example 1, which has the same innermost core compositionas Example 2, but a larger core of 28.1 mm, has sufficient durability tobe tested for the full 150 shots and more. Therefore, the larger corediameter has the unexpected result of improved durability withoutsacrificing driver performance (as reflected in the test data shown inFIG. 6.) This improved durability allows for core formulations thatcontain only HPF AD1035 and any desired additives, fillers, and meltflow modifiers, which was previously considered an undesirableformulation due to durability issues. However, with increased core size,believed by the inventors to be greater than 28 mm and 40 mm or less,the durability issues previously experienced in core formulationscontaining only HPF AD1035 and any desired additives, fillers, and meltflow modifiers were alleviated.

While various embodiments of the invention have been described, thedescription is intended to be exemplary, rather than limiting and itwill be apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible that are within the scopeof the invention. Accordingly, the invention is not to be restrictedexcept in light of the attached claims and their equivalents. Also,various modifications and changes may be made within the scope of theattached claims.

What is claimed is:
 1. A golf ball comprising: an inner core layerencompassing a center of the golf ball, a first intermediate layercomprising a rubber composition positioned radially outward of the innercore layer, and a cover layer positioned radially outward of the firstintermediate layer; wherein the inner core layer comprises a highlyneutralized polymer and has a diameter between 28 mm and 40 mm and a JISC hardness between about 65 and about 75; wherein the golf ball furthercomprises a second intermediate layer, wherein the second intermediatelayer is positioned radially outward of the first intermediate layer andsubstantially surrounds the first intermediate layer; and wherein thesecond intermediate layer has a flexural modulus of from 50,000 psi to100,000 psi and the cover layer has a flexural modulus of from 200 psito 3,000 psi.
 2. A golf ball comprising: an inner core layerencompassing a center of the golf ball, a first intermediate layercomprising a rubber composition positioned radially outward of the innercore layer, and a cover layer positioned radially outward of the firstintermediate layer; wherein the inner core layer comprises a highlyneutralized polymer and has a diameter between 28 mm and 40 mm and a JISC hardness between about 65 and about 75; wherein the golf ball furthercomprises a second intermediate layer, wherein the second intermediatelayer is positioned radially outward of the first intermediate layer andsubstantially surrounds the first intermediate layer; and wherein thesecond intermediate layer has a first flexural modulus and the coverlayer has a second flexural modulus, wherein the ratio of the firstflexural modulus to the second flexural modulus is from 10 to
 30. 3. Agolf ball comprising: an inner core layer encompassing a center of thegolf ball, a first intermediate layer comprising a rubber compositionpositioned radially outward of the inner core layer, and a cover layerpositioned radially outward of the first intermediate layer; wherein theinner core layer comprises a highly neutralized polymer and has adiameter between 28 mm and 40 mm and a JIS C hardness between about 65and about 75; wherein the golf ball further comprises a secondintermediate layer, wherein the second intermediate layer is positionedradially outward of the first intermediate layer and substantiallysurrounds the first intermediate layer; and wherein the secondintermediate layer has a first flexural modulus and the cover layer hasa second flexural modulus, wherein the ratio of the first flexuralmodulus to the second flexural modulus is from 25 to
 100. 4. A golf ballcomprising: an inner core layer encompassing a center of the golf ball,a first intermediate layer comprising a rubber composition positionedradially outward of the inner core layer, and a cover layer positionedradially outward of the first intermediate layer; wherein the inner corelayer comprises a highly neutralized polymer and has a diameter between28 mm and 40 mm and a JIS C hardness between about 65 and about 75;wherein the golf ball further comprises a second intermediate layer,wherein the second intermediate layer is positioned radially outward ofthe first intermediate layer and substantially surrounds the firstintermediate layer; and wherein the second intermediate layer has afirst flexural modulus and the cover layer has a second flexuralmodulus, wherein the ratio of the first flexural modulus to the secondflexural modulus is from 95 to 250.